Many methods and devices have already been disclosed to that end.
U.S. Pat. No. 5,626,651 describes a process and a system of that type according to which the turbulent gas stream flows above a series of plates defining non turbulent zones where the particles are collected. More precisely, the plates are parallel to each other and vertical. A filtering means made of fibers can also be provided between said plates in order to improve filtration notably of the finer particles.
International patent application WO-95/28,217 describes a device based on the same principle, but according to which the plates are provided with slots or replaced by grates. Frames covered with wire mesh containing a fibrous mat are also used in this prior art.
Furthermore, patent application WO-97/00,102 relates to a separator placed at the exhaust of diesel engines in order to collect the particles contained in the exhaust gas. A honeycomb structure pierced with channels perpendicular to the opening of the honeycomb cells is preferably provided. The porosity of such a structure is of the order of 70%. However, this device cannot be used for fogs because the droplets trapped in the cells cannot be removed by drainage.
International patent application PCT/FR-97/00,164 relating to a separator with one or more vertical drains laterally delimited by fibrous corrugated elements is also known. An agglomerator is also necessarily placed upstream from the separator in order to have larger particles that can be separated at the level of the separator. This is therefore relatively expensive and implies quite significant pressure drops.
However, these well-known means do not allow effective collection and removal of particles and/or droplets smaller than about one micrometer. In U.S. Pat. No. 5,626,651, the particles captured accumulate on the walls, then fall onto the bottom of the device under the effect of gravity. Means intended to shake the walls are often necessary to cause the particles accumulated on the walls to fall. This device poses problems when very fine particles smaller than one micrometer are to be separated. In fact, in this case, the height of the drain must be very limited and the plates must therefore be very high so that the equipment is very bulky for a very small section of flow. The same problem exists in the device according to document WO-95/128,217.
In patent application WO-97/00,102, the particles collected are oxidized.